Bees floral visitors, potential pollinators of cotton (Gossypium hirsutum L.) in agro-ecological farming

This study was conducted in July 2010 in the town of ChorÃ- CE, to evaluate the bees visiting the flowers of cotton (Gossypium hirsutum L. cv. CNPA - 7MH) in two agroecological crops. To do so, assessed the diversity of insects in two areas, their frequency, foraging behavior and potential pollinators of the culture, and studied the floral biology and pollination requirements of the specie CNPA - 7mH. Twenty-three species of bees visited the flowers of cotton, but Apis mellifera L. was not collected. Among the 22 species collected, eleven were common to both areas, only four in Area I and Area II in only seven. In area I the most represented families in number of species were Apidae and Halictidae, with 46.67% each. The least represented was Megachilidae, with 6.67% of the species. In Area II, Halictidae were the most represented, with 66.67% of the species, followed by Apidae, with 27.78%, and Megachilidae the least represented with 5.56%. Regarding the number of individuals, the most abundant family in the area I was APID with 48.00% of the subjects, followed by Megachilidae Halictidae with 32.00% and 20.00%. In Area II, APID was also the most abundant, with 39.62% of the specimens, followed by the Halictidae with 35.85% and Megachilidae with 24.53%. Diversity indices (Shannon-Weaver) of bees visiting the flowers of the cotton plant showed significant difference (p <0.05) among the areas. The observations of frequency and foraging behavior showed that only A. mellifera L., Lithurgus huberi Ducke and species of Halictidae Ceratinini when grouped and presented expressive activity. The results showed statistical differences (p <0.05) for the frequency of visitation among the bees and among the areas throughout the day. Observations of floral biology of the specie have shown that the anthesis flowers occurred from 7:00 pm and the stigmas were receptive at the time of anthesis and throughout the morning. Concerning to the requirements of pollination it was observed that there were significant differences (p <0.05) for the treatments, with free pollination and manual cross they did not differ from each other, but both avenging significantly more fruit than the manual self-pollination and restricted pollination. It was concluded that the expressive richness of bees visiting the flowers of the cotton areas was influenced by the agro-ecological cropping system and conservation of areas surrounding the plantations and that although the plantations of cotton (Gossypium hirsutum L. cv. CNPA - 7MH) is an autogamous species, spontaneous self-pollination is able to produce economically viable crops regardless of biotic pollinators, they are able to promote cross-pollination and contribute to increases the pollination of this crop. In addition, the cultivation of agroecological cotton proved being important for Lithurgus huberi as a food source but also as a place of rest, shelter and mating, being necessary to investigate the negative impacts of traditional crops of cotton on populations of this and other solitary bee species.O presente trabalho foi realizado no mÃs de Julho de 2010 no municÃpio de Chorà â CE, objetivando estudar as abelhas visitantes florais do algodoeiro (Gossypium hirsutum L. cv. CNPA â 7MH), em dois plantios agroecolÃgicos. Para tanto, avaliaram-se a diversidade destes insetos nas duas Ãreas, suas freqÃÃncias, comportamentos de forrageio e potencial polinizador da cultura, bem como estudaram-se a biologia floral e os requerimentos de polinizaÃÃo da cultivar CNPA â 7MH. Vinte e trÃs espÃcies de abelhas visitaram as flores do algodoeiro, mas Apis mellifera L. nÃo foi coletada. Entre as 22 espÃcies coletadas, onze foram comuns Ãs duas Ãreas, quatro exclusivamente na Ãrea I e sete apenas na Ãrea II. Na Ãrea I as famÃlias mais representadas em quantidade de espÃcies foram Apidae e Halictidae, com 46,67% cada uma. A menos representada foi Megachilidae, com 6,67% das espÃcies. Na Ãrea II, Halictidae foi a mais representada, com 66,67% das espÃcies, seguida de Apidae, com 27,78%, sendo Megachilidae a menos representada com 5,56%. Quanto ao nÃmero de indivÃduos, a famÃlia mais abundante na Ãrea I foi Apidea com 48,00% dos indivÃduos, seguida de Megachilidae com 32,00% e Halictidae com 20,00%. Na Ãrea II, Apidea tambÃm foi a mais abundante, com 39,62% dos espÃcimes, seguida por Halictidae com 35,85% e Megachilidae com 24,53%. Os Ãndices de diversidade (Shannon-Weaver) de abelhas visitantes florais do algodoeiro apresentaram diferenÃa significativa (p<0.05) entre as Ãreas. As observaÃÃes de freqÃÃncia e comportamento de forrageio mostraram que apenas A. mellifera L., Lithurgus huberi Ducke e espÃcies de Halictidae e Ceratinini quando agrupadas apresentaram atividade expressiva. Os resultados mostraram diferenÃas estatÃsticas (p<0,05) para as freqÃÃncias de visitaÃÃo entre as abelhas e entre as Ãreas ao longo do dia. As observaÃÃes da biologia floral da cultivar mostraram que a antese das flores acontecia a partir das 7:00h e os estigmas se mostravam receptivos no momento da antese e durante toda a manhÃ. No que se refere aos requerimentos de polinizaÃÃo observou-se que houve diferenÃas significativas (p < 0,05) para os tratamentos, com a polinizaÃÃo livre e a cruzada manual nÃo diferindo entre si, mas ambas vingando significativamente mais frutos que a autopolinizaÃÃo manual e a polinizaÃÃo restrita. Concluiu-se que a expressiva riqueza de abelhas visitantes florais do algodoeiro nas Ãreas estudadas foi influenciada pelo sistema de cultivo agroecolÃgico e conservaÃÃo dos entornos dos plantios e que apesar do algodoeiro (Gossypium hirsutum L. cv. CNPA - 7MH) ser uma espÃcie autÃgama, de autopolinizaÃÃo espontÃnea e capaz de produzir colheitas economicamente viÃveis independentemente de agentes polinizadores biÃticos, estes sÃo capazes de promover polinizaÃÃo cruzada e contribuir para incrementos na polinizaÃÃo desta cultura. AlÃm disso, o cultivo de algodÃo agroecolÃgico mostrou-se importante para Lithurgus huberi como fonte de alimento, mas tambÃm como local de descanso, abrigo e acasalamento, sendo necessÃrio investigar os impactos negativos de cultivos tradicionais de algodÃo sobre as populaÃÃes dessa e de outras espÃcies de abelhas solitÃrias